If it is a 'knock off' it would likely be a 'copy' of presumably a well known and succesful design (otherwise why bother). It has little in commom with the Prachen designs which are mould blown and have prunts with an impressed pattern.

Prunts have been used for decoration for thousands of years, at least as far back as the Romans.

A rather nice bowl to my eye but I have no idea when or where it would have been made.

the base is smooth polished and not the rough type you find on a lot of Chinese stuff. The prunts are simple blobs of blue glass and not impressed or moulded with anything like the raspberry shapes you sometimes see. Also the top rim has a slightly wobbly edge, not cut smooth.

I've been coming across a few Blenko pieces with prunts - designed by Wayne Husted and produced in 1959. None yet with this shape and colour of vase and it should be signed, but here's a catalogue page with a couple of examples:

http://www.blenkoarchive.org/Blenko_Catalogs/1959_13.jpg

More of the catalogue here: http://www.blenkoarchive.org/blenko_catalog_1959.htm